Boundary Potential and the Energy of Lipid Monolayer Compression at the Liquid Expanded State

IF 1.1 Q4 CELL BIOLOGY Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology Pub Date : 2021-06-10 DOI:10.1134/S1990747821020057

Yu. A. Ermakov

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引用次数: 3

Abstract—

Compression diagrams were obtained and analyzed for monolayers composed from DOPC, POPC, DMPC, DPPC, DPhPC, and DMPS at the surface of solutions containing KCl, CaCl₂, or BeCl₂ and in the presence of polylysine (PLL) or chlorpromazine (CPZ). Elastic properties of monolayers are characterized by the area of lipid molecules, presented as an incompressible area with a soft shell, the size of which exponentially depends on the lateral pressure and the coefficient of elasticity. This assumption describes well the shape of the lipid compression diagrams, including lipids with saturated hydrocarbon chains (DPPC and DMPS) in the region, where they exhibit liquid crystal properties (liquid expanded state, LE). All lipids show changes in the interfacial Volta potential in this region; these changes linearly depend on the effective value of the work applied to compress the monolayer. Choosing for zero value of the Volta potential its magnitude at the point with a lateral pressure of about 1 mN/m, the slope of linear section of this dependence was estimated. The slope of this dependence makes it possible to identify different types of membrane-active compounds affecting the elastic and electrostatic characteristics of the monolayer. It turned out that this slope is practically independent of the pH and ionic composition of the aqueous subphase but decreases upon adsorption of PLL polypeptides on the surface of the DMPS monolayer. The adsorption of small positively charged CPZ molecules on this monolayer leads to the deviation in the potential vs work dependence from the linear. A quantitative description of this deviation is in a good agreement with the assumption that CPZ molecules are incorporated into the monolayer. Their contribution to the change in the energy of the monolayer and the Volta potential is determined by the amount of incorporated CPZ molecules, the effect of which on lateral pressure can be approximated by a function similar to the Boltzmann relation.

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液体膨胀状态下脂质单层压缩的边界势和能量

摘要:在含有KCl、CaCl2或BeCl2的溶液表面，在聚赖氨酸(PLL)或氯丙嗪(CPZ)存在下，获得并分析了DOPC、POPC、DMPC、DPPC、DPhPC和DMPS组成的单层膜的压缩图。脂质分子的面积表征了单层膜的弹性特性，脂质分子的面积表现为具有软壳的不可压缩区域，其大小指数依赖于侧压力和弹性系数。这个假设很好地描述了脂质压缩图的形状，包括在该区域具有饱和烃链(DPPC和DMPS)的脂质，在那里它们表现出液晶性质(液体膨胀状态，LE)。所有脂类均在该区域界面伏特电位发生变化;这些变化线性地依赖于用于压缩单层的功的有效值。选取在侧压力约为1 mN/m的点处的伏特电位的大小为零值，估计其线性段的斜率。这种依赖性的斜率使得识别影响单层弹性和静电特性的不同类型的膜活性化合物成为可能。结果表明，该斜率实际上与水相的pH和离子组成无关，但在DMPS单层表面吸附PLL多肽时，该斜率减小。带正电的CPZ小分子在该单层上的吸附导致电位与功的线性关系偏离。这种偏差的定量描述与CPZ分子被纳入单层的假设很好地一致。它们对单层能量和伏特电位变化的贡献是由掺入CPZ分子的数量决定的，其对侧压力的影响可以用类似玻尔兹曼关系的函数来近似。

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来源期刊

Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology CELL BIOLOGY-

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1.40

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期刊介绍： Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology is an international peer reviewed journal that publishes original articles on physical, chemical, and molecular mechanisms that underlie basic properties of biological membranes and mediate membrane-related cellular functions. The primary topics of the journal are membrane structure, mechanisms of membrane transport, bioenergetics and photobiology, intracellular signaling as well as membrane aspects of cell biology, immunology, and medicine. The journal is multidisciplinary and gives preference to those articles that employ a variety of experimental approaches, basically in biophysics but also in biochemistry, cytology, and molecular biology. The journal publishes articles that strive for unveiling membrane and cellular functions through innovative theoretical models and computer simulations.